Synthesis and catalytic activity of Ag nanoparticles dispersed on nitrogen-doped GOPx toward direct electrooxidation of formaldehyde

Modulating Silver Performance in Electrocatalytic Oxidation of HCHO via SMSI between Ag-Co3O4 Interfaces

The replacement of oxygen evolution reactions with organic molecule oxidation reactions to enable energy-efficient hydrogen production has been a subject of interest. However, further reducing reaction energy consumption and releasing hydrogen from organic molecules continue to pose significant challenges. Herein, a strategy is proposed to produce hydrogen and formic acid from formaldehyde using Ag/Co3O4 interface catalysts at the anode. The key to improving the performance of Ag-based catalysts for formaldehyde oxidation lies in the strong SMSI achieved through the well-designed "spontaneous redox reaction" between Ag and Co3O4 precursors. Nano-sized Ag particles are uniformly dispersed on Co3O4 nanosheets, and electron-deficient Agδ+ are formed by the SMSI between Ag and Co3O4. Ag/Co3O4 demonstrates exceptional formaldehyde oxidation activity at low potentials of 0.32 V versus RHE and 0.65 V versus RHE, achieving current densities of 10 and 100 mA cm-2, respectively. The electrolyzer "Ag/Co3O4||20% Pt/C" achieves over 195% hydrogen efficiency and over 98% formic acid selectivity, maintaining stable operation for 60 hours. This work not only presents a novel approach to precisely modulate Ag particle size and interface electronic structure via SMSI, but also provides a promising approach to efficient and energy-saving hydrogen production and the transformation of harmful formaldehyde.

Recent Advances in Electrochemical Sensors for Formaldehyde

Formaldehyde, a ubiquitous indoor air pollutant, plays a significant role in various biological processes, posing both environmental and health challenges. This comprehensive review delves into the latest advancements in electrochemical methods for detecting formaldehyde, a compound of growing concern due to its widespread use and potential health hazards. This review underscores the inherent advantages of electrochemical techniques, such as high sensitivity, selectivity, and capability for real-time analysis, making them highly effective for formaldehyde monitoring. We explore the fundamental principles, mechanisms, and diverse methodologies employed in electrochemical formaldehyde detection, highlighting the role of innovative sensing materials and electrodes. Special attention is given to recent developments in nanotechnology and sensor design, which significantly enhance the sensitivity and selectivity of these detection systems. Moreover, this review identifies current challenges and discusses future research directions. Our aim is to encourage ongoing research and innovation in this field, ultimately leading to the development of advanced, practical solutions for formaldehyde detection in various environmental and biological contexts.

Highly Sensitive Detection of Formaldehyde by Laser-Induced Graphene-Coated Silver Nanoparticles Electrochemical Sensing Electrodes

Formaldehyde (HCHO) poses a grave threat to human health because of its toxicity, but its accurate, sensitive, and rapid detection in aqueous solutions remains a major challenge. This study proposes a novel electrochemical sensor composed of a graphene-based electrode that is prepared via laser induction technology. The precursor material, polyimide, is modified via the metal ion exchange method, and the detective electrode is coated with graphene and silver nanoparticles. And the special structure of graphene-coated Ag was demonstrated using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS) results show that graphene provides more sites for Ag NRs to be exposed and increases the surface area of contact between the solution and the detection object. In addition, differential pulse voltammetry (DPV) analysis exhibits high linearity over the HCHO concentration range from 0.05 to 5 μg/mL, with a detection limit of 0.011 μg/mL (S/N = 3). The Ag NPs in the electrochemical reaction will adsorb the intermediate •CO and •OH, catalyze their combination, and finally convert to CO2 and H2O, respectively. A microdetection device, specially designed for use with commercial micro-workstations, is employed to fully demonstrate the practical application of the electrode, which paves a way for developing formaldehyde electrochemical sensors.

Influence of solvent molecular geometry on the growth of nanostructures

Solvent properties such as surface tension, dielectric constant, and viscosity have been extensively studied over more than 150 years to understand their influence on the growth kinetics of nanostructures. Interestingly, these nanoparticles-based studies have missed the influence of solvent molecular geometry. Herein, by synthesizing ZnO nanorods on a highly conductive nitrogen incorporated graphene oxide (N-GO) substrate, we present the first study showing the influence of solvent molecular geometry on the growth mechanism of nanostructures. The solvents such as water (N-GO-ZnO-W) allow a large number of functional atoms along a, b and c-axis to coordinate in all possible directions with the metal ions of wurtzite hexagonal crystal system of ZnO and thus leads to lower aspect ratio nanorods. On the contrary, the unavailability of binding sites along a-axis for solvents such as ethanol (N-GO-ZnO-E) provides a size-limiting effect and leads to preferred growth along b and c-axis, thus generating ZnO nanorods with a higher aspect ratio. The study shows that the number of interacting atoms, carbon chain length and the solvent molecular geometry influence the aspect ratio and therefore a solvent could be used to tune the nanostructures morphology and hence the performance of devices based on them.

The insight study of SnO pico size particles in an ethanol-water system followed by its biosensing application

Pico sized Stannous oxide particles (SnO PPs) were synthesized in an ethanol-water solvent system on the surface of nitrogen doped graphene oxide (GO). The highly conductive support was a combination of dual interactions between 4-aminomethylbenzylamine (AMBA) and GO. The oppositely positioned -NH₂ linkers of the AMBA were covalently incorporated into the GO matrix through condensation reaction followed by the strong π - π stacking interactions between aromatic rings of AMBA and GO. The change in the local chemical environment of GO via dual interactions provided a suitable atmosphere for the growth and dispersion of SnO PPs on GO-AMBA surface. The possible mechanism for the formation of SnO in an ethanol-water solvent system was evaluated. Furthermore, a light was shed on the factors responsible for the pico size of SnO particles synthesis along with its phenomenal distribution on the GO-AMBA surface. The catalyst containing SnO PPs was deployed as a biosensor for the detection of ascorbic acid (AA) for the very first time. A very wide linear range of 5.0 × 10^-5-7.0 × 10^-3 M, limit of detection (LOD) of 1.19 × 10^-5 M along with excellent practical feasibility, storage stability, repeatability and selectivity towards AA electrooxidation showed the excellent synergy between nitrogen-rich GO surface and SnO PPs. The sensitivity (885.54 µAmM^-1cm^-2) of the catalyst was the most attractive feature, as it was obtained in the presence of 5 and 2-fold higher concentration of UA and DA interfering species respectively.